The invention concerns a spherical safety rotor of a fuse for a spinning projectile with a recess on the surface of the sphere or ball to lock the rotor in the safety position. An axially continuous retaining chamber of the ball carries the detonating means and has two opposing orifices. A first cut-out in the spherical surface adjacent to the first orifice reduces the mass of the ball.
A safety rotor of this type is described in German Patent DE-OS No. 32 24 749, the disclosure of which is incorporated herein by reference. The cut-out in the ball reduces the mass of the rotor only slightly. In addition, the cut-out is located on the rotor so that when the ball is in the safety position it only partially covers a detonating passage, which detrimentally affects the safety of the fuse. That is, there exists the possibility that communication can occur between the charge in the detonating passage and the detonator in the ball, via the cut-out.
It has been discovered that as the result of unavoidable tolerances, the center of gravity of the rotor is usually off-center. During the rotation of the projectile, the rotor then moves out of the true center in the fuse. Consequently, differential frictional forces occur between the rotor and the surrounding bearing shell of the fuse. Higher frictional forces thus act against the pre-set moment of the rotor which is to impel the rotor from the safety position to the ignition position. Under certain unfavorable conditions these opposing frictional forces may lead to the failure of the rotor.
It is an object of the invention to provide a rotor of the afore-mentioned type wherein the displacement of the rotor from the safety position to the ignition position is facilitated without detrimentally affecting fuse safety.
According to the invention, this object is attained with a rotor of the above-mentioned type by that at least one second cut-out is provided adjacent to the second orifice in the surface of the ball, in order to reduce the mass of the rotor. The reduction in mass of the rotor decreases the frictional forces generated between the rotor and its bearing in the case of untrue rotation. Accordingly, these forces act only slightly against the set-up moment of the rotor, so that the latter is able to become erected safely.
By means of the distribution of the mass-reducing cut-outs of the rotor, a favorable distribution of the surface zones of the ball serving to support it, may be obtained. The cut-outs may be arranged so that the safety functions of the rotor are not affected. It is, therefore, an object of the invention to provide the rotor with mass-reducing cut-outs without reducing the safety of the fuse.